Respiratory therapy may require the delivery of drugs directly to the lungs. The drugs conventionally prescribed are bronchodilators and inhalable steroids. Bronchodilators dilate the airways of the lungs by causing the smooth muscles of the airways to relax. Steroids reduce the swelling of inflammatory, allergic tissues of the airways. Some of the drugs typically prescribed are Alupent, Brethaire, Proventil, Ventolin and Albuterol.
Such respiratory drugs are typically delivered to the lungs via medication nebulizers which convert a liquid medication into a mist form. Nebulizers are conventionally connected in the inspiratory line running from a mechanical ventilator.
Respiratory drugs are also delivered in aerosol form from metered dose inhalers. Aerosol medication may be sprayed directly into the mouth, into a hand held spacer such as the AEROCHAMBER.RTM. available from the Monaghan Medical Corporation, or directly into an inspiratory line with or without the aid of a spacer. One in-line spacer for connection into an inspiratory line is the AeroVent holding chamber available from the Monaghan Medical Corporation. The AeroVent holding chamber includes an accordian-like cylindrical wall which is expandable when an aerosol medication is delivered and which is collapsable after the medication has been dispensed. After it is collapsed, the AeroVent holding chamber remains connected in the inspiratory line and an internal conduit delivers fluid through the chamber. When medication is to be dispensed, the chamber folds out lengthwise and the conduit separates into two portions to create a spacer or holding chamber.
Whether aerosol medication or liquid medication by a nebulizer is being delivered to the lungs, particle size of the aerosolized medication is important. The greater the particle size, the greater the chance of loss of the medication by impaction on the inner walls of the spacer, inspiratory line, and upper airways where medication is ineffective. The smaller the particle size, the greater the potential that the medication will be carried to the more peripheral airways where the medication is effective.
One of the problems with a spacer having a cylindrical accordian-like wall is that it may expand or contract radially and axially. The resulting change in pressure and volume in the inspiratory line may cause a disruption in the operation of the mechanical ventilator which is set to respond to inspiratory efforts by a patient.
Another problem is that biocontaminated water may stand in the holding chamber when collapsed and provide an environment conducive to the growth of bacteria. When collapsed, fluid flows not through the holding chamber itself, but through an internal conduit. With moist air flowing through the internal conduit, moisture may migrate into the holding chamber upon expansion to contribute to the growth of bacteria.
Still another problem is that a cylindrical spacer is not directly connectable to a parallel wye connection without kinking the parallel wye connection or expiratory tube. Extensions may be inserted between the parallel wye connection and the cylindrical spacer, but extensions are undesirable because the spacer is thus disposed further from the lungs, thereby adding another piece of equipment and increasing the chances for impaction on the inner surfaces of the additional equipment.